Embodiments presented herein relate generally to electric machines, and more particularly, to a permanent magnet machine having a plurality of fractional-slot concentrated windings where each coil is wound around a single stator tooth.
Electric machines, for example, permanent magnet machines with fractional-slot concentrated windings generally include a stator with a core that is provided with a plurality of slots. A plurality of windings is wound around the slots of the stator. A rotor is disposed within the stator and includes a plurality of permanent magnets. The machine operation typically includes injecting current to the stator windings that would subsequently generate a torque in the rotor.
One advantage of such a machine is the generation of a smooth torque. Another advantage of the electric machine is a higher fault-tolerant capability, allowing the machine to work even in faulty conditions. When the stator windings are excited, a magnetic field is induced around the stator. This magnetic field generates a high content of magneto motive force (MMF) harmonics. When the machine is in operation, the magnetic field induced around the stator with the high MMF harmonics interacts with the magnetic field around the rotor. The presence of stator MMF harmonics may generate unbalanced forces and torque ripples, resulting in losses in the machine.
There is a need for an improved electric machine.